Because prior research suggests that resource allocation among parks varies by neighborhood SES, we propose to undertake a national longitudinal study of the existence of disparities in park management practices in 25 representative US cities and 200 parks. In order to advance the state of science on the influence of park management practices on physical activity and park use and to shape public policy on health promotion at the population level, we propose an investigation with the following specific aims: 1) To determine whether there are systematic differences in park resources, programming, management practices, and park use depending upon the socioeconomic status of park neighborhoods in a representative sample of American cities, 2) To determine whether changes in resource allocation among parks in these cities are distributed equally among high and low income parks, or whether allocation changes attempt to address health disparities among potential park users. We will also determine whether changes in resource allocation are accompanied by changes in park-based physical activity, and 3) To make recommendations to the Departments of Parks and Recreation in each city that will support greater use of park facilities among populations who may experience health disparities that can be ameliorated by physical activity. To accomplish the aims of this investigation, we will train a cadre of park professionals and members of community-based organizations that support neighborhood parks to act as citizen scientists and collect objective data. Engaging these citizen-scientists in the research process is intended to increase local capacity to reliably measure park management practices, park characteristics, park use, and physical activity. Citizen-scientists are an asset that will endure long after the proposed research (if funded) is completed and could form the basis for research in which future interventions to promote physical activity can be rigorously evaluated. We will also interview key stakeholders to assess other factors that may impact local park use.